Synthesis and characterization of a Ni nanoparticle stabilized on Ionic liquid‐functionalized magnetic Silica nanoparticles for tandem oxidative reaction of primary alcohols

In this research, preparation of the magnetic nanoparticle, coating by a silica shell using (3‐aminopropyl) triethoxysilane and synthesis of a novel sulfonic acid‐substituted imidazolium‐based ionic liquid onto the surface of these particles via a multi‐component reaction, is described. The functionalized nanoparticles was loaded by Ni nanoparticles and characterized by means of techniques such as XRD, FTIR, SEM, EDX, TEM, TGA and ICP‐OES. The nanostructures have spherical shapes that ranged in size from 80 to 100 nm. The catalytic activity of these nanoparticles was tested in aerobic oxidation of primary alcohols that showed good performance in the wide range of primary alcohols in water at mild reaction conditions. As a second step of this work, the tandem oxidative synthesis of alkylacrylonitriles and bisindolylmethanes were investigated using primary alcohols under oxidation conditions. This catalyst system can be recovered using external magnet and reused for five consecutive cycles without significantly less of its activity.     

Multivariate linear regression with missing values

This contribution presents and discusses an efficient algorithm for multivariate linear regression analysis of data sets with missing values. The algorithm is based on the insight that multivariate linear regression can be formulated as a set of individual univariate linear regressions. All available information is used and the calculations are explicit. The only restriction is that the independent variable matrix has to be non-singular. There is no need for imputation of interpolated or otherwise guessed values which require subsequent iterative refinement.     

Electropolymerized coatings of poly(o‐anisidine) and poly(o‐anisidine)‐TiO2 nanocomposite on aluminum alloy 3004 by using the galvanostatic method and their corrosion protection performance

Poly(o‐anisidine) (POA) and poly(o‐anisidine)‐TiO₂ (POA‐TiO₂) nanocomposite coatings on aluminum alloy 3004 (AA3004) have been investigated by using the galvanostatic method. The electrosynthesized coatings were characterized by FT ‐ IR spectroscopy, XRD, SEM ‐ EDX and SEM. The corrosion protection performance of POA and POA‐TiO₂ nanocomposite coatings was investigated in the 3.5% NaCl solution by using potentiodynamic polarization technique and electrochemical impedance spectroscopy. The results show that the corrosion rate of the nanocomposite coatings is about 900 times lower than the bare AA3004 under optimal conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Potential of Biocellulose Nanofibers Production from Agricultural Renewable Resources: Preliminary Study

In the present preliminary study, we report results for the biocellulose nanofibres production by Gluconacetobacter xylinus. Production was examined by utilizing different feedstocks of single sugars and sugar mixtures with compositions similar to the acid hydrolyzates of different agriculture residues. Profiles for cell proliferation, sugar consumption, and the subsequent pH changes were thoroughly analyzed. Highest biocellulose production of 5.65 g/L was achieved in fructose medium with total sugar consumption of 95.57%. Moreover, the highest production using sugar mixtures was 5.2 g/L, which was achieved in feedstock with composition identical to the acid hydrolyzate of wheat straws. This represented the highest biocellulose yield of 17.72 g/g sugars compared with 14.77 g/g fructose. The lowest production of 1.1 and 1.75 g/L were obtained in xylose and glucose media, respectively, while sucrose and arabinose media achieved relatively higher production of 4.7 and 4.1 g/L, respectively. Deviation in pH of the fermentation broths from the optimum value of 4–5 generally had marked effect on biocellulose production with single sugars in feedstock. However, the final pH values recorded in the different sugar mixtures were ～3.3–3.4, which had lower effect on production hindrance. Analyzing profiles for sugars' concentrations and cell growth showed that large amount of the metabolized sugars were mainly utilized for bacterial cell growth and maintenance, rather than biocellulose production. This was clearly observed with single sugars of low production, while sugar consumption was rather utilized for biocellulose production with sugar mixtures. Results reported in this study demonstrate that agriculture residues might be used as potential feedstocks for the biocellulose nanofibres production. Not only this represents a renewable source of feedstock, but also might lead to major improvements in production if proper supplements and control were utilized in the fermentation process.     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT−GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, α, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4 ± 0.5 s⁻¹ and 0.51, respectively at pH = 7.0. The obtained results indicate that hydrazine peak potential at OMWCNT−GCE shifted for 14, 109, and 136 mV to negative values as compared with oxadiazole-modified GCE, MWCNT−GCE, and activated GCE surface, respectively. The electron transfer coefficient, α, and the heterogeneous rate constant, k′, for the oxidation of hydrazine at OMWCNT−GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0 μM and 10.0 to 400.0 μM and detection limit of 0.17 μM for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT−GCE was shown to be successfully applied to determine hydrazine in various water samples.

     

Fabrication and characterization of calix[4]arene Langmuir–Blodgett thin film for gas sensing applications

Microwave irradiation has been found to be a highly efficient method for etherification of p-tert-butylcalix[4]arene with alkyl bromides or ditosylate. The corresponding products were obtained as a pure form in modest yield within short reaction time when the reactions were performed under microwave irradiation.     

Supercritical carbon dioxide extraction and analysis of lipids from <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> using gas chromatography

The influence of six different supercritical carbon dioxide extraction conditions on the quantity and quality of the extracted lipids from Chlorella vulgaris (C. vulgaris) was examined using experimental design. The investigated parameters included dynamic extraction times (45 and 90 min), pressures (300 and 350 bars) and a modifier (with and without ethanol). By using a grinding method prior to the extraction, cells were disrupted resulting in an enhanced extraction yield. The results showed that the total lipid yields increased by increasing the pressure, extraction time and the modifier. Applying harsher extraction conditions increased the extraction of longer-chain fatty acids (FAs), changed the FA compositions and enhanced the total lipid yield. Using transesterification, the extracted lipids were converted to biodiesel. The biodiesel physiochemical properties were estimated using empirical equations based on the fatty acid methyl ester contents. Furthermore, analysis of the protein content of remaining biomass showed a decrease in protein content with increasing the lipid extraction yield.     

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT?GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k _s, and the charge transfer coefficient, ??, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4?±?0.5?s^?1 and 0.51, respectively at pH?=?7.0. The obtained results indicate that hydrazine peak potential at OMWCNT?GCE shifted for 14, 109, and 136?mV to negative values as compared with oxadiazole-modified GCE, MWCNT?GCE, and activated GCE surface, respectively. The electron transfer coefficient, ??, and the heterogeneous rate constant, k??, for the oxidation of hydrazine at OMWCNT?GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0???M and 10.0 to 400.0???M and detection limit of 0.17???M for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT?GCE was shown to be successfully applied to determine hydrazine in various water samples.